Driveline slip yokes for drive shaft assemblies include a plug that is inserted into an open end face near a universal joint. The slip yoke has an internal bore at the open face that includes a splined surface that mates with a spline shaft member. The plug covers exposed ends of the splines. Traditionally, the plug includes a central circular hole that is defined by an axis parallel to a centerline of the splines. This hole compensates for pressure generated within the slip yoke due to axial movement of the spline shaft member within the internal bore.
When the spline shaft member moves outward to extend the length of the drive shaft assembly, a vacuum is created within a cavity that is formed between an end of the spline shaft member and the plug. Similarly, when the spline shaft member moves inward to shorten the length of the drive shaft assembly, pressure is formed within the cavity between the end of the spline shaft member and the plug. The central circular hole in the plug allows for movement of air inward and outward to equalize pressure between the outside and inside the slip yoke assembly. If the spline shaft member is moved outwardly, the slip shaft assembly can become contaminated at the spline shaft member seal interface because of the vacuum created in the cavity. If the increase of atmospheric pressure is not equalized when the spline shaft member is moved inward, the plug inserted in the end of the slip yoke can be pushed out of position, which would expose the splines to potential contamination in addition to allowing leakage of lubricating fluids.
One disadvantage with this current configuration is that with the current circular hole configuration, the hole itself is a leak path for external contaminants such as water, salt, dirt, etc. Thus, there is a need for an improved slip yoke plug configuration.